This research project was conducted in the Ottawa-Carleton region of Ontario to provide information on reasons why students did not participate in a Grade 7 hepatitis B school immunization project, and to determine whether telephone contact increased attendance at the community catch-up clinics above that achieved by a notice sent home with the child from school. A matched comparison group design was used. The overall uptake of the first dose of the vaccine in the region was 94% of 8,560 eligible students; 90% were immunized at the school clinic and 4% at the community catch-up clinic. About 4% of the parents refused to have their child immunized at the school or catch-up clinics. Of parents in the intervention group 198 (95%) were contacted by phone. The major reasons for non-participation at the school clinics were: (1) the child was not at school on the clinic day, or the child was sick (51%), (2) there were problems with the consent form (21%), and (3) the parents did not know of the program (10%). More students from the intervention group (72%) came for vaccination than did those of the control group (50%) (p